Adds a new entry with the given name and value.
An up.Params instance can hold multiple entries with the same name.
To overwrite all existing entries with the given name, use up.Params#set() instead.
var params = new up.Params()
params.add('foo', 'fooValue')
var foo = params.get('foo')
// foo is now 'fooValue'
The name of the new entry.
The value of the new entry.